SOSP generally holds the highest prestige for its exclusive focus on operating system principles. ASPLOS and EuroSys have broader scopes, encompassing system architecture and programming languages. HotOS focuses more specifically on operating systems design and implementation.
Kernel: Session 177, Session 176
SOSP and USENIX ATC are highly relevant for Android Kernel topics such as memory management, scheduling algorithms, file systems, security mechanisms, and virtualization technology.
Also, check arXiv (not peer-reviewed), maintained by Cornell University.